Browsing by Author "Ntusi, Ntobeko"

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    Abnormal myocardial perfusion correlates with impaired systolic strain and diastolic strain rate in systemic lupus erythematosus: a cardiovascular magnetic resonance study
    (BioMed Central Ltd, 2015) Ntusi, Ntobeko; Sever, Emily; Lockey, Joseph; Francis, Jane; Piechnik, Stefan; Ferreira, Vanessa; Matthews, Paul; Wordsworth, Paul; Neubauer, Stefan; Karamitsos, Theodoros
    Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder that commonly affects the heart, resulting in a 7 to 9 times greater incidence of cardiovascular disease (CVD) in SLE patients compared to healthy controls. Female patients with SLE between 35 and 44 years old have an incidence of myocardial infarction over 50 times greater than that observed in the Framingham cohort. The clinical utility of cardiovascular magnetic resonance (CMR) first-pass perfusion for assessment of myocardial ischaemia is well-established. We hypothesised that CMR including stress first-pass perfusion would be able to detect coronary microvascular disease and subtle functional abnormalities in SLE and aimed to detect myocardial ischaemia in SLE using adenosine stress perfusion CMR.
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    Cardiac Magnetic Resonance to Detect the Underlying Substrate in Patients with Frequent Idiopathic Ventricular Arrhythmias
    (2021-06-18) Nikolaidou, Chrysovalantou; Kotanidis, Christos P; Wijesurendra, Rohan; Leal-Pelado, Joana; Kouskouras, Konstantinos; Vassilikos, Vassilios P; Karvounis, Haralambos; Ntusi, Ntobeko; Antoniades, Charalambos; Neubauer, Stefan; Karamitsos, Theodoros D.
    Background: A routine diagnostic work-up does not identify structural abnormalities in a substantial proportion of patients with idiopathic ventricular arrhythmias (VAs). We investigated the added value of cardiac magnetic resonance (CMR) imaging in this group of patients. Methods: A single-centre prospective study was undertaken of 72 patients (mean age 46 ± 16 years; 53% females) with frequent premature ventricular contractions (PVCs ≥ 500/24 h) and/or non-sustained ventricular tachycardia (NSVT), an otherwise normal electrocardiogram, normal echocardiography and no coronary artery disease. Results: CMR provided an additional diagnostic yield in 54.2% of patients. The most prevalent diagnosis was previous myocarditis (23.6%) followed by possible PVC-related cardiomyopathy (20.8%), non-ischaemic cardiomyopathy (8.3%) and ischaemic heart disease (1.4%). The predictors of abnormal CMR findings were male gender, age and PVCs/NSVT non-outflow tract-related or with multiple morphologies. Patients with VAs had an impaired peak left ventricular (LV) global radial strain (GRS) compared with the controls (28.88% (IQR: 25.87% to 33.97%) vs. 36.65% (IQR: 33.19% to 40.2%), p < 0.001) and a global circumferential strain (GCS) (−17.66% (IQR: −19.62% to −16.23%) vs. −20.66% (IQR: −21.72% to −19.6%), p < 0.001). Conclusion: CMR reveals abnormalities in a significant proportion of patients with frequent idiopathic VAs. Male gender, age and non-outflow tract PVC origin can be clinical indicators for CMR referral.
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    Cardiovascular magnetic resonance characterisation of the phenotype of resistant uncontrolled hypertension
    (2019) Letuka, Pheletso; Ntusi, Ntobeko; Rayner Brian
    Background: Resistant hypertension (RH) is defined as blood pressure (BP) that remains elevated (>140/90mmHg) despite being treated with an antihypertensive regimen of 3 or more medications from different classes, including a long-acting calcium channel blocker, an angiotensin converting enzyme inhibitor or angiotension receptor blocker and a diuretic. The prevalence of RH in South Africa is currently unknown, however, clinical reports suggest that it is not rare. Patients with RH are significantly predisposed to cardiovascular (CV) diseases compared to patients with controlled BP. Consequences of RH include left ventricular hypertrophy, heart failure, ischaemic heart disease, chronic kidney disease leading to end-stage renal disease, stroke, vascular dementia, CV death and peripheral arterial disease. A proportion of patients with RH who never achieve BP control despite maximal medical treatment, represent a potentially novel and distinctive phenotype which is different from RH patients whose BP canbe controlled. Recognising and categorising such patients becomes the initial and crucial step in stratifying phenotypes and defining mechanisms of treatment resistance. Objectives: The aim of this study was to identify patients with resistant uncontrolled hypertension (RUH) and compare phenotypes in these patients to resistant controlled hypertensives (RCH). Methods: We enrolled 50 patients from the Groote Schuur Hospital Hypertension Clinic: a teriary referral hospital for RH. Patients on 4 or more antihypertensive medication including a diuretic, with BP< 140/90mmHg were considered RCH, and those with BP ≥ 140/90 considered RUH. Assessments included clinical examination, electrocardiography, echocardiography, applanation tonometry, serum biomarkers and cardiovascular magnetic resonance (CMR - which included biventricular volumes and function, myocardial strain, tissue characteristics and late gadolinium enhancement - LGE). Results: Thirty were diagnosed with RUH and twenty with RCH. Patients with RUH were more likely to have a longer duration since diagnosis of hypertension (10.5±10.7 vs. 3.6±3.4, p=0.02) and more likely to be on treatment that included an ACE-inhibitor (90% vs. 58%, p=0.01). As expected, patients with RUH had significantly higher systolic BP (155.6±21.6 vs. 137.8±16.5 mmHg, p< 0.001), diastolic BP (88.4±14.5 vs. 77.5±13.6 mmHg, p= 0.03), mean arterial BP (115.4±17.2 vs 101±15.3 mmHg, p= 0.004) and pulse pressure (67.3±14.2 vs. 60.1±12.4 mmHg, p=0.001). Further, RUH patients had significantly lower large artery elasticity (12.5±4 vs 14.7±3.8ml/mmHgx100, p=0.08) and lower small artery elasticity (4.1±2.1 vs. 6.9±3.6ml/mmHgx100, p< 0.001). RUH patients also had a higher systemic vascular resistance (1754±418.4 vs. 1363±371.5dyneXsecXcm-5, p=0.002). On CMR, RUH patients had lower right ventricular (RV) end-systolic and end-diastolic volumes (p=0.02), as well as higher indexed left ventricular mass (LVMI) (61.6±17.6 vs 52.9±13.9 g/m2 , p= 0.06). There were no differences in native T1, extracellular volume quantification and LGE volume fraction between RUH and RCH patients. Conclusions: Patients with RUH have a greater involvement and more severe CV phenotype, that is likely to result in increased CV morbidity and mortality, including greater target end organ damage as a result of vascular adaptations and concentric remodeling.
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    Cardiovascular magnetic resonance in women with cardiovascular disease: position statement from the Society for Cardiovascular Magnetic Resonance (SCMR)
    (2021-05-10) Ordovas, Karen G; Baldassarre, Lauren A; Bucciarelli-Ducci, Chiara; Carr, James; Fernandes, Juliano L; Ferreira, Vanessa M; Frank, Luba; Mavrogeni, Sophie; Ntusi, Ntobeko; Ostenfeld, Ellen; Parwani, Purvi; Pepe, Alessia; Raman, Subha V; Sakuma, Hajime; Schulz-Menger, Jeanette; Sierra-Galan, Lilia M; Valente, Anne M; Srichai, Monvadi B
    Abstract This document is a position statement from the Society for Cardiovascular Magnetic Resonance (SCMR) on recommendations for clinical utilization of cardiovascular magnetic resonance (CMR) in women with cardiovascular disease. The document was prepared by the SCMR Consensus Group on CMR Imaging for Female Patients with Cardiovascular Disease and endorsed by the SCMR Publications Committee and SCMR Executive Committee. The goals of this document are to (1) guide the informed selection of cardiovascular imaging methods, (2) inform clinical decision-making, (3) educate stakeholders on the advantages of CMR in specific clinical scenarios, and (4) empower patients with clinical evidence to participate in their clinical care. The statements of clinical utility presented in the current document pertain to the following clinical scenarios: acute coronary syndrome, stable ischemic heart disease, peripartum cardiomyopathy, cancer therapy-related cardiac dysfunction, aortic syndrome and congenital heart disease in pregnancy, bicuspid aortic valve and aortopathies, systemic rheumatic diseases and collagen vascular disorders, and cardiomyopathy-causing mutations. The authors cite published evidence when available and provide expert consensus otherwise. Most of the evidence available pertains to translational studies involving subjects of both sexes. However, the authors have prioritized review of data obtained from female patients, and direct comparison of CMR between women and men. This position statement does not consider CMR accessibility or availability of local expertise, but instead highlights the optimal utilization of CMR in women with known or suspected cardiovascular disease. Finally, the ultimate goal of this position statement is to improve the health of female patients with cardiovascular disease by providing specific recommendations on the use of CMR.
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    Characterisation of cardiac protein changes post death: pilot study
    (2025) Mokaila, Dipolelo; Ntusi, Ntobeko; Taylor Laura; Ngwa Lumngwena, Evelyn; Martin, Lorna
    Background: Postmortem interval (PMI) is an important consideration in medicolegal death investigation. There are various approaches used in the estimation PMI also known as time since death. Methods such as temperature measurement, evaluation of muscle contraction, lividity and decomposition rate are applied to estimate PMI. These methods are however affected by environmental factors that either delay or accelerate some of the processes. Scientific evidence has revealed that the expression, concentration, and stability of proteins do not remain the same after death. This changing nor varied behaviour of proteins within the body has prompted number of research that characterise protein as a way to estimate time elapsed since death also known PMI. Furthermore, it is through interaction of proteins with other micro molecules that crucial signalling pathways and cellular processes are functional and often drive mechanisms leading to healthy and disease of organism, as a result these changes can be studied to gain insight into disease pathophysiology. There is a need to evaluate the structural integrity of tissues during the PM to see whether they might serve as a control for research. This implies that before using these tissues as controls, biomolecule stability in these tissues needed to be assessed. Therefore, it is equally crucial to investigate how these biochemical parameters change across brief PMIs in order to guide research on the selection of control tissues and their potential as an additional technique for PMI estimation. We aimed to understand biochemical changes that occur postmortem in cardiac tissues through analysis of proteins. Moreover, to determine if there was degradation in cardiac proteins post death for bodies with known time since death. Additionally, to determine the usability of PM cardiac tissues as controls for research from cardiac protein integrity over time PM. Methods: This was a cross-sectional, observational, and descriptive study. Changes in native cardiac troponin Cardiac troponin I, vinculin, and eukaryotic elongation factor (eEf1a) and their degradative products were evaluated in cardiac tissue using Western blot(WB) assay from decedents recruited at the Salt River Mortuary(SRM), Cape Town. The native and degradative products of these proteins were compared between samples collected at different times postmortem to determine whether and how much each protein has degraded. Image J analysis of protein intensities of native bands and degradative products were used to compare proteins from different PMI. Results: Recruited and sampled 52 decedents. 30 cases were sampled at PMI of greater than 72 while only 22 were sampled at PMI of less than 72 hours . Our western blot detection of 117kda vinculin protein showed this to be present in all left ventricle(LV) samples analyses. The degradation of this protein commenced at 37 hours and progressed with time in LV and could be detected beyond 3 days. In aortic valve (AV) this protein was intact in tissues extracted from living individuals and cases with early PMI of less than 24 hours. Mitral valve vinculin protein was detected from 8-57 hours postmortem and could not detect this protein beyond 91-hours. This protein in MV protein didn't show any evidence of degradation bands. cardiac troponin T native protein in LV was present in all investigated cases. This protein showed degradation bands in all cases with intensity increasing as time progressed. Cardiac troponin I detection in LV was present in majority of the cases expect for 48 and 57 case which may be due to improper sample handling or storage. However, this did not depict any degradation band but there was evidence of decrease in the native band intensity with increasing PMI hours. Lastly, we detected for eEfa1 in LV, and we found this to be present in majority of cases and the band intensities also decreased with increasing PMI. Conclusion: The aim of the study was to understand biochemical changes that occur postmortem in cardiac tissues through analysis of biochemical molecules. The results showed change of proteins in tissues with progressed time in postmortem. This may suggest that these protein biomarkers may be suitable to be used in PMI estimation. Additionally, the study noted integrity of protein at < 8 hours in postmortem depicting that cases sampled at that time may be suitable to be utilised as control for research.
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    Characterisation of phenotypes of inflammation, fibrosis and remodeling in chronic rheumatic heart disease using multiparametric cardiovascular magnetic resonance and autophagy markers
    (2023) Aremu, Olukayode Olasunkanmi; Ntusi, Ntobeko; Skatulla, Sebastian
    Background: Rheumatic heart disease (RHD), concomitant to valvular damage, heart failure, arrhythmias and pulmonary hypertension is the major source of cardiovascular morbidity and mortality in the young, predominantly in low- and middle-income countries (LMICs). We investigated the association of valve lesions in RHD with cardiovascular magnetic resonance (CMR) tissue characteristics and autophagy markers, in this study. Methods: Forty-seven (47) patients (42 ± 12.8 years), with advanced RHD, awaiting valve replacement, confirmed on echocardiography, and matched with 30 healthy controls (39 ± 12.1 years), were scanned using a 3T Siemens Magnetom Skyra. CMR parameters were derived from the following acquisitions: cine imaging of the short and long axes, T1 mapping (MOLLI, 5(3)3, estimation of ECV and late gadolinium enhancement (LGE) imaging. For the cellular study, we analysed the immunoexpression of Beclin, LC3, p62, BAX, Bcl-2 and caspase-3 in patients confirmed with RHD and valvular heart disease
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    Correlation of signal-averaged electrocardiogram and late gadolinium enhancement cardiovascular magnetic resonance in the detection of myocardial fibrosis in arrhythmogenic right ventricular cardiomyopathy and other myocardial disorders
    (2021) Mgidlana, Msimelelo Mzwamadoda; Ntusi, Ntobeko; Kraus, Sarah
    Background. The diagnosis of fibrotic scar tissue in arrhythmogenic right ventricular cardiomyopathy (ARVC) and other cardiomyopathies is crucial as it forms the substrate for ventricular tachycardia (VT) and fibrillation (VT). Signal-averaged electrocardiography (SAECG) abnormalities are frequent in ARVC and in other cardiomyopathy-related ventricular arrhythmias. The correlation between cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) and parameters of SAECG in ARVC is not known. Method. Thirty-five patients [median age 32 years (IQR 25 – 46)] referred to the ARVC Registry at Groote Schuur Hospital were included in this retrospective study. SAECG was performed with high-amplification and filtered using bidirectional Butterworth filters between 40 and 250 Hz. A filtered averaged QRS (fQRS) was obtained and analysed for fQRS duration, low amplitude signal duration <40 mV (LAS40), and root-mean-square voltage in the last 40ms of the QRS (RMS40). LGE acquired at 5 to 20 minutes after intravenous administration of gadolinium (0.1mmol/kg to 0.2mmol/kg of body mass) was assessed. We evaluated the correlation between SAECG parameters and the presence of LGE. Results. Sixteen patients had definite ARVC, 5 had possible ARVC, 4 had idiopathic VT/VF, 2 had Athlete's heart, 1 had dilated cardiomyopathy (DCM), 1 had hypertrophic cardiomyopathy (HCM), 1 had SVT and 1 had pericardial constriction. LGE was present in 13 (81%) ARVC patients, 2 (40%) with possible ARVC, 1 (50%) with athlete's heart and in all patients with DCM and HCM. Patients with idiopathic VT/VF, pericardial constriction and supraventricular tachycardias had no myocardial LGE on CMR. Comparing patients with LGE and those without LGE on CMR, there were no differences in fQRS, (114ms [102.3 – 119] versus 111ms [99.5 -130], p = 0.608); LAS40 (34.5ms [16.8 - 40.8] versus 31ms [27.5 – 45], p = 0.566) and a RMS40 (23.5 µV [14.3 – 47.5] versus 33 µV [18.5 – 43.5], p= 0.621), respectively. LGE was present in 6 (60%) patients who had VT at presentation, in 9 (56%) with VT at baseline or follow-up and in all (2) patients who survived cardiac arrest. Three oneway analyses of variance (fQRS vs LGE, LAS40 vs LGE and RMS40 vs. LGE) confirmed that there was no correlation between LGE technique on CMR and SAECG for the detection of myocardial fibrosis in ARVC and other myocardial disorders: for fQRS F(1 , 33) = 1.47, p = 0.23,  2 = 0.02; for LAS40 F(1 , 33) =0.95, p = 0.34,  2 = 0.02 and for RMS40 F(1 , 33) = 0.36, p= 0.85,  2 = 0.02. Conclusion. In this study comparing assessment of myocardial fibrosis by LGE CMR and SAECG, there was no correlation between CMR and SAECG in detection of myocardial fibrosis in ARVC and other cardiovascular diseases.
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    Genealogical tracing of founder variants linked to cardiomyopathies in a South African cohort
    (2025) Houghton, Abbey; Shaboodien, Gasnat; Ntusi, Ntobeko
    Introduction: Cardiomyopathies are a major cause of heart failure in South Africa, yet their prevalence, causes, and outcomes remain poorly understood. The IMHOTEP registry was established to clinically and genetically characterise affected patients and through this study several common pathogenic variants were identified, suggesting potential founder variants. This study aimed to genealogically trace the origins of these variants in the probands and their families. Methods: Participants were recruited from South African tertiary hospitals, with baseline data recorded at enrolment. Next generation sequencing identified several probands with possible founder variants which prompted haplotype construction and genealogical tracing. Variants were identified in the genes PKP2, LMNA, BAG3 and TTN and three microsatellite markers, spanning the 5', intergenic and 3' regions, were designed for each of the genes of interest in order to perform haplotype analysis. Genealogical data was collected using online resources, genealogy databases, and the voter's roll. Results: Five PKP2 c.1162C>T (p.Arg388Trp), BAG3 c.925C>T (p.Arg309Ter), LMNA c.568C>T (p.Arg190Trp), TTN c.87624C>G (p.Tyr29208Ter), and TTN c.95008C>T (p.Arg31670Ter) possible founder variants were identified in 38 probands (12 probands with the PKP2 variant; 3 probands with BAG3 variant, three probands with LMNA variant and 20 probands with the two TTN variants). PKP2 was traced to Afrikaner families of Dutch/French Huguenot descent from the 1600s. BAG3 was linked to French-Huguenot and Canadian ancestry. LMNA tracing was limited due to the number of families as well as limited Mixed-Ancestry family records. TTN variants had issues with haplotyping and genealogical challenges as well as limited records for Black African and Mixed-Ancestry families. Conclusions: This research significantly advances our understanding of cardiomyopathy genetics in South Africa. The identification of Dutch/French and French-Canadian ancestries associated with the PKP2 and BAG3 variants, respectively, provides valuable insights into the historical origins and population-specific genetic landscape of these cardiomyopathies. This ancestral information not only deepens our understanding of cardiomyopathy in the region but also has important implications for risk assessment and genetic counselling. By identifying common progenitors, we can better target screening efforts and provide more accurate risk assessments for individuals carrying these founder variants
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    Impaired energetics and normal myocardial lipids in rheumatoid arthritis and systemic lupus erythematosus: a phosphorous and proton magnetic resonance spectroscopy and cardiovascular magnetic resonance study
    (BioMed Central Ltd, 2015) Ntusi, Ntobeko; Holloway, Cameron; Francis, Jane; Davis, Anne; Levelt, Eylem; Piechnik, Stefan; Ferreira, Vanessa; Matthews, Paul; Wordsworth, Paul; Karamitsos, Theodoros; Neubauer, Stefan
    Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) commonly involve the cardiovascular system and are associated with significant morbidity and mortality, driven by cardiovascular inflammation, microvascular and diastolic dysfunction and fibrosis. Cardiovascular magnetic resonance (CMR) can assess non-invasively cardiac function, strain, ischaemia, altered vascular function, perfusion, inflammation and fibrosis; magnetic resonance spectroscopy (MRS) provides further insights into the status of myocardial energetics and lipidosis. To date, there have been no cardiovascular MRS studies in RA and SLE patients. We hypothesised that RA and SLE would be associated with impaired myocardial energetics and lipidosis.
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    Impaired myocardial perfusion in rheumatoid arthritis is associated with impaired strain, strain rate, disease activity and myocardial oedema: a cardiovascular magnetic resonance study
    (BioMed Central Ltd, 2015) Ntusi, Ntobeko; Sever, Emily; Lockey, Joseph; Francis, Jane; Piechnik, Stefan; Ferreira, Vanessa; Matthews, Paul; Wordsworth, Paul; Neubauer, Stefan; Karamitsos, Theodoros
    Rheumatoid arthritis (RA) commonly involves the cardiovascular system, and is associated with significant morbidity and mortality. Mechanisms of cardiovascular disease (CVD) involvement are not fully understood, but cardiovascular inflammation is thought to drive many of the CVD manifestations, including myocardial ischaemia. The clinical utility of CMR first-pass perfusion for assessment of myocardial ischaemia is well-established. The aim of this study was to assess whether RA patients without known epicardial coronary artery disease have evidence of myocardial hypoperfusion.
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    Impaired myocardial perfusion is associated with extracellular volume expansion, disease activity and impaired strain and strain rate in systemic sclerosis: a cardiovascular magnetic resonance study
    (BioMed Central Ltd, 2015) Ntusi, Ntobeko; Sever, Emily; Lockey, Joseph; Francis, Jane; Piechnik, Stefan; Ferreira, Vanessa; Matthews, Paul; Wordsworth, Paul; Neubauer, Stefan; Karamitsos, Theodoros
    Systemic sclerosis (SSc) is characterised by vascular dysfunction and multi-organ fibrosis, with the heart commonly involved. Cardiovascular disease (CVD) in SSc may be direct or indirect, but often remains subclinical. SSc patients with apparent cardiovascular clinical features are at greater risk of deterioration and premature cardiovascular death, often from complications of myocardial ischaemia. CMR first-pass perfusion detects myocardial ischaemia with great accuracy. We hypothesised that CMR first-pass perfusion would be able to differentiate between segmental (indicating epicardial coronary artery disease) and non-segmental subendocardial (indicating microvascular dysfunction) perfusion defects in patients with SSc; and that microvascular dysfunction (relating to chronic myocardial inflammation) was more frequent in SSc.
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    Investigation of circulatory and tissue-specific metabolomic biomarkers in valvular heart disease using mass spectrometry
    (2025) Mutithu, Daniel Wakiri; Ntusi, Ntobeko; Naidoo, Richard; Skatulla, Sebastian
    The work presented in this thesis was based on an investigation of the circulatory and tissue specific metabolic biomarkers in patients with rheumatic heart disease (RHD) and degenerative aortic stenosis (AS), compared to matched, healthy controls. The study hypothesis was that cardiac tissue obtained from heart valve biopsies from RHD and degenerative AS patients would have distinct histological features. The second hypothesis was that severe RHD and degenerative AS patients have distinct serum and tissue specific metabolic profiles. The third hypothesis was that pathologic regions on heart valves would have distinct spatial metabolomic profiles compared to non-diseased regions of the valves. Whole blood samples were collected from matched participants with a diagnosis of RHD and degenerative AS, as well as matched controls recruited from the Cardiac Clinic at Groote Schuur Hospital. Valve tissue samples were collected from patients undergoing valve replacement surgery at Groote Schuur Hospital. Haematoxylin and eosin staining was used to assess the histopathological features of the heart valves. Untargeted metabolomics was performed on serum and valve tissues using ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry. In-situ biomarker localisation was performed with matrix assisted laser desorption ionisation mass spectrometry imaging. Univariate and multivariate statistical analyses was used to explore covariation with the potential metabolomic biomarkers and bioinformatics tools used to explore the gene-metabolite interactions. The study had several key observations. First, though rare, we reported that chronic RHD may be admixed with features of acute rheumatic fever, within the same patient. Second, using an untargeted/discovery approach, we identified metabolites involved in the major energetic pathways, amino acids metabolism, and inflammation regulation which were altered in RHD and degenerative AS. The identified biomarkers were associated with cardiovascular imaging-based remodelling parameters. Third, RHD patients with single or double valve replacement, and degenerative AS patients demonstrated distinct tissue-specific metabolic signatures. Metabolites involved in amino acid, fatty acid, and crucial biomolecule metabolism were associated with histopathological and cardiovascular imaging-based parameters of valvular heart disease. Finally, tissue-specific metabolites could be localised on valve biopsies obtained from RHD and degenerative AS participants, though no differences were observed between the two group.
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    Outcomes of patients with hypertensive heart disease and heart failure with reduced ejection fraction (HFrEF) at a tertiary centre in South Africa
    (2022) Boakye, Darlene; Kraus, Sarah; Ntusi, Ntobeko; Davidson, Bianca
    Introduction. Hypertension is endemic in Sub-Saharan Africa and has been shown to be the leading cause of heart failure (HF) on the continent. Clinical observation suggests that hypertensive heart disease (HHD) is potentially reversible with medical therapy and that baseline characteristics and outcomes differ from other causes of HF. Method. This was a single centre, retrospective hospital-based observational study of patients diagnosed with HF with reduced and mid-range ejection fraction (HFrEF and HFmrEF) secondary to HHD, seen at the Cardiomyopathy Clinic at Groote Schuur Hospital over a threeyear period. Ethics approval was obtained (HREC REF 677/2018). Results. A total of 59 patients were included, with an equal representation of both genders [female 49.2%]. The majority of patients were of mixed race [57.6%] and black African [39%] ethnicity. The mean age at presentation was 44 ±12.0 years. At baseline, 71.7% of patients had effort intolerance [NYHA Class II, 36.2%; Class III, 32.8%; Class IV, 1.7%] and the most common symptoms were dyspnoea [65.5%], pedal oedema [34.5%] and orthopnoea [29.3%]. A pre-existing diagnosis of hypertension was present in 66.8%, 30,5% had other comorbidities (HIV, 5 [8.5%]; diabetes mellitus, 5 [8.5%]; chronic kidney disease, 5 [8.5%]) and 62% of women presented in the peripartum period. At baseline, the mean systolic and diastolic blood pressures were 130±20.1 and 81±12.8mmHg, respectively. Congestive HF was observed in 40.7% of cases despite being on medical therapy (loop diuretics [88.5%]; ACE-I [88.5%]; beta blocker [84.6%]; MRA [51.9%]). Atrial fibrillation [3.5%] and LBBB [10.5%] were infrequent. Left ventricular hypertrophy (LVH) was noted in 54.4% on ECG, and the mean QTc was prolonged [466±35ms]. On echocardiogram, mean wall thickness was normal [IVSd 1.0 [0.9-1.2]; LVPWd 1.1 [0.8-1.3], however, left atrial [4.4±0.9cm] and LV end-diastolic dimensions [LVEDD 6.4±0.8cm] were increased. LV ejection fraction (EF) was markedly impaired [29.9±10.4%]. At follow up, there was a significant (p< 0.001). Recovery of LVEF was observed in 86.5% patients where repeat imaging was done [LVEF ≥ 50% in 45.9%; LVEF improved ≥10% in 40.5%]. 1- and 3-year transplant-free survival was 98.3% and 90.5%, respectively. Conclusion. Most patients with HHD and impaired LVEF have a pre-existing history of hypertension and present with effort intolerance, congestion and mildly elevated or ‘pseudonormal' blood pressures. Concentric LVH was not a prominent feature on echocardiogram and AF was infrequent. Despite severely impaired LVEF at baseline, mortality was lower than expected for HF patients and improvement in LVEF on therapy was observed in the majority of patients.
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    Predictors of diffuse myocardial fibrosis in HIV infected persons: A multiparametric cardiovascular magnetic resonance study
    (2019) Saad, Hadil; Ntusi, Ntobeko; Alhamud, Ali
    With the advent of effective antiretroviral therapy (ART), human immunodeficiency virus (HIV) is now a chronic disease. With increasing survival, cardiovascular disease (CVD) in people living with HIV is increasing in the ART era, with a changing epidemiology that is now largely characterised by diastolic dysfunction. Our hypothesis was that ART would be associated with regression of myocardial fibrosis in HIV. Myocardial fibrosis is associated with an unfavourable outcome in many different clinical settings. In this study, we used cardiovascular magnetic resonance (CMR) measurements of extracellular volume fraction (ECV) and tissue characterisation to assess diffuse myocardial fibrosis and determine the effect of ART use on diffuse myocardial fibrosis in HIV infected individuals on ART compared to untreated HIV infected persons. Forty-four asymptomatic individuals with no known CVD who were HIV infected were included and classified into two groups: 25 on ART for >1 year (60% male, mean age 40 ± 9 years) and 19 ART-naïve (37% male; mean age 36 ± 8 years). All patients underwent CMR on a 3T Siemens Skyra scanner. Imaging included cine, T2 weighted (STIR), native T1 and T2 mapping, late gadolinium imaging (LGE) and ECV imaging. HIV infected patients not on ART had a median time from diagnosis to entry in the study of 9 months. Treated patients had been stable on ART for over 12 months. There was no difference in left ventricular volumes, mass and function between treated and untreated HIV-infected patients. We found that, while elevated in both groups, the native T1 values were lower in the treated group compared to untreated patients. Again, while elevated in both groups, the ECV was slightly lower in the treated group, this did not reach statistical significance. There was no correlation between native T1 value or ECV with either disease duration or nadir CD4 count. There was no difference in left ventricular volumes, mass and function between treated and untreated HIV-infected patients. We found that, while elevated in both groups, the native T1 values were lower in the treated group compared to untreated patients. Again, while elevated in both groups, the ECV was slightly lower in the treated group, this did not reach statistical significance. There was no correlation between native or ECV with either disease duration or nadir CD4 count. We conclude that in patients with HIV, diffuse myocardial fibrosis provides valuable insights into the pathophysiology of HIV associated CVD and mechanism of diastolic dysfunction. Importantly, in this study, with a short lead period on ART, ART was associated with regression of diffuse myocardial fibrosis, as assessed by native T1, but not by ECV. Larger prospective studies are needed with longer follow-up to assess the role of CMR in both risk stratification and in tracking disease progression in HIV.
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    Targeted re-sequencing of a large South African cardiomyopathy cohort
    (2024) Ndibangwi, Polycarp; Shaboodien, Gasnat; Ntusi, Ntobeko
    Introduction: Cardiomyopathy is a major cause of heart failure and transplantation globally. In sub Saharan Africa, cardiomyopathies are ranked as the third greatest contributing cause of cardiovascular diseases and account for about 30% of adults hospitalised with heart failure. The prevalence of heart failure due to cardiomyopathies is not well established in the South African population. To address this knowledge gap, we aimed to study the genetic cause of the disease in a large cohort of South African patients with cardiomyopathy. Design: We recruited participants from multiple centres in South Africa and Mozambique between 2015 and 2022. Cases were classified according to phenotypes by a team of experts. Using the Illumina platform, we used targeted sequencing on a panel of 38 known genes that cause primary cardiomyopathies. We used the ACMG classification to investigate class 3, 4 and 5 variants. Variants were validated using Sanger sequencing. Result: We recruited 690 cardiomyopathy probands (594 adults and 96 paediatrics). The 594 adults include dilated cardiomyopathy (n=450), hypertrophic cardiomyopathy (n=60), restrictive cardiomyopathy (n=43) and arrhythmogenic cardiomyopathy (n=41) probands. The adult DCMs constituted 75.8% (450/594) of the IMHOTEP study. The DCM probands had a mean age of 35.6 years at diagnosis, and a 56% preponderance of females were seen; the dominant populations recruited were Black-African (58%) and Mixed ancestry (33%). We reported a diagnostic yield of 16.9% (76/450) for the DCM probands, where 68.4% of the probands had pathogenic TTN truncating variants. The adult HCM cohort constituted 10.1% (60/594) of the IMHOTEP study probands, with a mean age of 41.3 years at diagnosis and a male preponderance of 65%. The dominant populations recruited were 57% Mixed and 25% Black-African. The diagnostic yield for the adult HCM cohort was 23.3% (14/60), with MYH7 (40%) and MYBPC3 (27%) found to be the predominant genes. The adult RCM cohort constituted 7.2% (43/594) of the IMHOTEP study probands, with a mean age of 33.0 years at diagnosis and a 65% female preponderance. The dominant populations recruited were 81% Black-African and 12% Mixed ancestry. We reported a diagnostic yield of 9.3% (4/43) for the RCM probands. The adult ACM cohort constituted 6.9% (41/594) of the IMHOTEP study probands, with a mean age of 40.6 years at diagnosis and a 65.9% male preponderance. The dominant populations recruited were 66% White and 20% Mixed ancestry. We reported a diagnostic yield of 29.3% (12/41), with PKP2 accounting for 62% of the variants. Meanwhile, paediatric probands constituted 13.9% (96/690) of the IMHOTEP study, and 70% were Black-Africans. The diagnostic yield for the paediatric cohort was 2.1% (2/96). Conclusion: This study summarises the findings of the largest cardiomyopathy cohort in Africa. We show a very low genetic yield across all cohorts and that most probands are younger than reported internationally. We also report that DCM has emerged as the dominant phenotype in South Africa. EMF and RCM were categorised as restrictive cardiomyopathies; however, this study identified no single genetic cause in the Mozambique cohort. This study highlights that there is still much work to be done as we have only identified the genetic cause of disease in a small proportion of cardiomyopathy patients.
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    The molecular genetics of familial cardiomyopathy
    (2023) Kamuli, Stephen Nzeki; Shaboodien, Gasnat; Ntusi, Ntobeko
    Introduction The cardiomyopathies are responsible for approximately 5.9 of 100,000 deaths in the general global population and in sub-Saharan Africa (SSA), these myocardial diseases are observed in 21.4% of patients with heart failure. The precise etiology of the cardiomyopathies is currently not well known and through our research we aim to contribute to the genetic landscape and bridge the gaps in knowledge for the different cardiomyopathies as SSA could provide some very important insights into the cardiomyopathies and identify other possible disease mechanisms. Methods Through next generation sequencing techniques such as whole exome sequencing and targeted resequencing we studied three South African families with severe cardiomyopathy. Clinical diagnosis and recruitment of cardiomyopathy patients into the study was done at Groote Schuur Hospital, Cape Town by a panel of experts. Next generation sequencing data was analysed and filtered through various stringent criteria and the final list of variants were validated through Sanger sequencing. Results In the first multi-generational family with severe dilated cardiomyopathy (DCM) (DCM 334), we identified a pathogenic DMPK c.1067C>T(p.P356L) variant in the proband and her affected father. We also screened a cohort of 542 cardiomyopathy probands though Sanger sequencing of the DMPK gene and identified the DMPK c.1477C>T(p.R493C) variant as a variant of unknown significance. We then investigated a three-generation family with four affected family members who were also affected with severe DCM (DCM343). We used whole exome sequencing and identified the pathogenic BAG3 c.925C>T (p.R309Ter) variant as the cause of disease within this family. Viral infection, anti-hypertensive medication and genetic modifiers in RYR1 and NEB contributed to the variable phenotype among the individuals with the BAG3 variant. Through targeted resequencing we also identified the same pathogenic BAG3 variant in 2 of the 634 cardiomyopathy probands screened. In the third family, we investigated a South African family affected with severe arrhythmogenic cardiomyopathy (ACM). We used whole exome sequencing and targeted resequencing in combination and identified the pathogenic PKP2 c.2197_2202InsGdelCACACC (p.H733Afs*8) as the cause of disease in the proband and his father. We also present evidence of the ALPK3 c.2701C>T(p.Q901Ter) variant modifying the phenotypic manifestation which correlates with the variable penetrance that is seen among ACM families. Conclusion Through this project, we have identified many firsts. To the best of our knowledge, we are the first to show that DMPK is associated with primary DCM in severely affected young patients. As a first for South Africa, we not only identified the pathogenic BAG3 variant in a family with severe DCM, but we also identified the same variant in two additional probands, raising the possibility of a founder effect. In the third and final family with ACM, we identified the pathogenic PKP2 variant as the cause of disease within this family with the novel ALPK3 variant acting as a possible modifier. Our research has added to what is currently known about the cardiomyopathies in Africa but there is still much work to be done as we believe we have just scratched the tip of the iceberg.
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    The Rationale, Design and Implementation of the African Cardiomyopathy and Myocarditis Registry
    (2019) Kraus, Sarah; Ntusi, Ntobeko; Mayosi, Bongani
    Background. Causes of heart failure in Africa are largely non-ischaemic: hypertension, rheumatic heart disease and cardiomyopathy. Cardiomyopathies pose a great challenge because of poor prognosis and high prevalence in low- and middle-income countries with limited access to specialised care. Little is known about aetiology or outcomes of cardiomyopathy in Africa. Method. The African Cardiomyopathy and Myocarditis Registry Program (IMHOTEP) is a pan-African multi-centre, hospital-based cohort study. It aims to describe the clinical characteristics, aetiology, genetics, management and outcome of cardiomyopathies in children and adults. Index patients were recruited as either incident (new) or prevalent (existing) cases, and family screening was conducted in selected cases. Several sub-studies were conducted at the initiating centre, including; outcome studies on prevalent cases incorporated into IMHOTEP, a cardiovascular magnetic resonance (CMR) study on incident cases, and a clinical genetics study on families. Results. The pilot phase was commenced in Cape Town (February 2015), followed by staggered initiation at 6 further sites. Over 600 index patients have been recruited to the registry to date. Preliminary data on the first 99 incident adult cases recruited at the initiating site, showed that dilated cardiomyopathy (DCM; n=67) was commonest, followed by hypertrophic (HCM; n=13), left ventricular noncompaction (LVNC; n=11), restrictive (RCM; n=4) and arrhythmogenic right ventricular (ARVC; n=4) cardiomyopathies. Cardiomyopathy occurred predominantly in mixed race (46%) and black (41%) Africans, and more frequently in females (54%). Mean age of presentation was 36.8 ±12.5 years. CMR performed in incident cases (67/99, 68%) proved diagnostically useful, however, acute myocarditis was only reported in one individual. In addition, prevalent cases with ARVC and DCM were enrolled from two existing studies at the initiating centre. Except for fewer (24%) genotype positive (PKP2 20%, CDH2 4%) individuals with ARVC (n=70), the baseline characteristics and diagnostic criteria were similar to what has been reported internationally. Transplant-free survival probability at 1-year, 5-years and 10-years was 98.5%, 90.7%, and 80.8% respectively in ARVC (median survival time 9.0 years) and there were no significant differences in survival between those with and without implantable cardioverter defibrillators [p=0.27]. In the prevalent DCM cohort (n=133), transplant-free survival probability was 93.4%, 82.2% and 73.1% at 1-year, 5-years and 10-years respectively, with a median survival time of 5.3 years. The age of onset (34.8 ±11.0 years) and death (41.5 ±9.6 years) were significantly younger in our DCM patients compared to European cohorts. Thirty-five families were recruited (16 genotype positive, 19 genotype unknown) with autosomal dominant inheritance observed in 94.3% families. Conclusion. IMHOTEP is the first multi-centre registry for cardiomyopathy in Africa. Preliminary data suggests an earlier age of onset compared to European cohorts and that DCM is the most common form of cardiomyopathy in South Africa. Molecular genetic analysis will provide vital and novel data on the genetic causes of cardiomyopathy in Africans.
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    The South African Cardiovascular Magnetic Resonance (SA-CMR) Registry: An Interim Analysis of Clinical Utility, Indications and Baseline Characteristics of Patients Undergoing CMR in a Single Centre in South Africa
    Coccia,Cecilia Beatrice Irene; Ntusi, Ntobeko
    Background Cardiovascular magnetic resonance (CMR) is a clinically useful imaging modality that is fast becoming a routine tool in clinical practice. In 2013, the results of the first multi-national registry, EuroCMR, were published. The study highlighted the clinical significance and impact of CMR in Europe. More recently, the global CMR registry (GCMR) has been established to standardise data from international centres in order to support the role of CMR across diverse patient demographics. Despite South Africa joining the GCMR network, the role of CMR in the South African context remains undefined and at present there is limited research pertaining to its use. The South African CMR (SA-CMR) registry was founded in 2016 with a view to gain insight into CMR in the South African setting. This interim analysis of the first 1,142 patients aims to establish the clinical use and indications for CMR, to assess the quality of CMR images and to the assess the baseline demographic and clinical characteristics of the cohort. Secondary objectives aim to ascertain the impact of CMR on patient management. Methods SA-CMR was designed to be a national registry that consists of both retrospective and prospective CMR data. This analysis reports on the single-centre experience at Groote Schuur Hospital, Cape Town. The retrospective arm consists of patients that underwent CMR at Groote Schuur Hospital (GSH) from its introduction in 2005 to April 2017. This interim analysis will assess the first 1,142 patients in this retrospective arm. Results Of the indications for use of CMR in Cape Town, the ascertainment of the presence of cardiomyopathies or their delineation accounted for 54% of scans performed. 15% were utilised to define congenital cardiac anomalies. The average age of patients undergoing CMR was 40 years old and there was a slightly increased percentage of female to male patients (52.65% vs 47.32%). Image quality was diagnostic in 99% of cases and adverse reactions from gadolinium contrast agent use only occurred in 0.18% of patients – of which none were fatal. 34% of scans showed either an alternative diagnosis or additive information which subsequently resulted in an alteration in clinical management of the patient. Conclusion In comparison with the European cohort, where the most important indication for CMR was risk stratification in suspected coronary artery disease, SA-CMR showed that, in the South African setting, CMR was utilised predominantly for investigation of cardiomyopathies. SACMR further supported CMR as a safe imaging technique which has assisted in diagnostics and clinical management of patients with cardiovascular disease in South Africa.
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    The utility of the 1994 versus the revised 2010 Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) Task Force diagnostic criteria for identifying mutation-positive probands with ARVC
    (2021) Lukhna, Kishal; Ntusi, Ntobeko; Kraus, Sarah
    Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disorder characterised by structural and functional abnormalities of the right ventricle with or without left ventricular involvement. In 1994, Task Force criteria (TFC) were proposed for the diagnosis of ARVC and were found to be highly specific but lacked sensitivity. In 2010, revised TFC were proposed to increase sensitivity and facilitate diagnosis in those with subtle phenotypes. Purpose: Many participants of ARVC registries have been enrolled using the 1994 TFC and not re-analysed using the 2010 TFC. We retrospectively compared the utility of both TFC for the diagnosis of mutation-positive probands in the IMHOTEP (The African Cardiomyopathy and Myocarditis Registry Program) study with the aim of identifying diagnostic changes that may have clinical impact. Method: 162 participants with the suspicion of ARVC were referred between May 2003 and May 2018 to our ARVC registry. 150 cases were reviewed using the same ECG and imaging data to fulfil both TFC, and were re-classified by a diagnostic panel at Groote Schuur Hospital, Cape Town. Results: Sixty-eight participants were diagnosed with ARVC by the diagnostic panel and included into the registry; 14/68 participants with ARVC were found to be mutation-positive. Eighty-two participants were found to have an alternative diagnosis or insufficient criteria and were excluded from the ARVC registry. Mutation-positive probands presented at a significantly younger age compared to the mutation-negative group (29 ± 14 years versus 39 ± 13 years, p=0.009), suggesting an earlier onset of ARVC. Common reasons for presentation in the mutation-positive cohort included palpitations (79%) and presyncope (64%), with Page 11 of 78 approximately twice the number of participants presenting with sustained ventricular tachycardia (VT) compared to mutation-negative participants (79% versus 47%, p=0.036). The diagnostic yield of the 2010 versus 1994 TFC (n=68) revealed more participants with a definite diagnosis, and less featuring in possible and no criteria categories. A 67% (n=8) change in diagnosis from 1994 borderline to 2010 definite, and an 88% (n=7) change from 1994 possible to 2010 borderline, were observed. Mutation-positive participants had a higher yield for definite ARVC when compared to mutation-negative participants. We subsequently analysed the contribution of each diagnostic modality at fulfilling TFC in our mutation-positive definite participants and found CMR contribution statistically significant, p=0.021. Conclusion: Our study found that mutation-positive probands were found to be younger, more likely to present with sustained VT, fulfilled a significantly larger number of major 2010 TFC than mutation-negative probands, and that the 2010 TFC for structural and repolarisation abnormalities were more useful in diagnosing ARVC compared to 1994 TFC. We found a significant evolution in classification between both TFC, suggesting that re-classification of participants recruited in traditional ARVC registries according to updated criteria is worthwhile.
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    Whole-exome sequencing of cases with familial cardiomyopathy
    (2021) Spracklen, Timothy; Ntusi, Ntobeko; Shaboodien Gasnat
    Introduction: Cardiomyopathies are disorders of the myocardium that can lead to heart failure, arrhythmias and sudden death. Heritable forms include dilated, hypertrophic and arrhythmogenic cardiomyopathy (DCM, HCM and ACM respectively). As heterogeneous disorders, over 50 genes have been implicated in these cardiomyopathies to date. However, the yield of genetic testing ranges from less than 40% in idiopathic DCM to over 50% in ACM and HCM, indicating that many causal genes are yet to be identified. This is particularly true in African populations, where the genetics of cardiomyopathy is underexplored. In a review of the role of next-generation sequencing in gene discovery, over 20 new cardiomyopathy genes were found to have been identified through exome sequencing of cardiomyopathy patients. The literature review also highlighted the need for functional validation of newly identified disease genes. Therefore, the aims of this investigation were to utilise exome sequencing to identify disease-causing mutations in South African families with heritable cardiomyopathy, and to establish methods of variant validation through functional modelling in zebrafish. Methods: Five probands and 34 relatives were included in this investigation. The probands and their relatives were clinically examined and diagnosed with DCM, HCM or ACM at Groote Schuur Hospital, Cape Town. Exome sequencing was performed on each of the five probands as well as at least one other family member. Variants of interest were identified by filtering the exome sequencing data by allele frequency, variant quality, variant consequence, predicted deleteriousness, and the potential inheritance patterns as determined by family history analysis. Variants occurring in known cardiomyopathy genes were prioritised, but genes outside the cardiac panel were considered based on literature mining, expression in the heart, and results of prior animal models. Candidate variants were validated by Sanger sequencing and assessed using international criteria for pathogenicity. The candidate ACM gene POLG was investigated in zebrafish larvae using two genetic manipulations. Firstly, zebrafish polg was disrupted using CRISPR/Cas9 in single-cell embryos and, at three days post-fertilisation, the phenotypic effects were compared to uninjected control larvae, as well as larvae in which other known cardiomyopathy genes were disrupted. Secondly, human POLG cDNA was cloned, and the c.2942A>G variant introduced using site-directed mutagenesis; this construct was used to generate variant POLG mRNA that was injected into zebrafish embryos. Larvae were phenotypically examined at four days post-fertilisation and compared to three control groups (unmutated POLG-injected, water-injected, and uninjected embryos). Results: In three families, genotype-phenotype correlations were identified that have not yet been reported in South Africa, although this genetic overlap between cardiomyopathies has been described elsewhere. Family 1: the mutation MYH7 c.4394C>T (p.S1465L) was identified in three siblings with DCM. Although MHY7 is typically associated with HCM, mutations in this region have been reported in DCM patients in other populations. Family 2: the mutation GLA c.774_775del (p.R259Rfs*5) was found in a mother and her son, both of whom had been diagnosed with HCM. The finding of a pathogenic truncating GLA mutation in this family resulted in the genetic rediagnosis of those individuals with Fabry disease, an HCM phenocopy. Family 3: in this large DCM family consisting of three affected brothers and their nephew, no pathogenic variants were identified, but two variants of uncertain significance (VUSs) were found in the genes DSC2 and PKP2. Both variants fulfilled some criteria for pathogenicity, but have not been associated with DCM in South African patients before. In Families 4 and 5, no mutations in known cardiomyopathy-causing genes were identified. Family 4: exome sequencing revealed the variant POLG c.2492A>G (p.Y831C) in this ACM family, with a clinical phenotype consisting of arrhythmia and left ventricular fibrosis. This was a VUS, but in vivo modelling using CRISPR/Cas9 in zebrafish larvae demonstrated that disruption of the gene may impair cardiac development, while expression of the c.2492A>G variant in zebrafish larvae resulted in a significant reduction in heart rate, ventricle size and cardiac output. These results indicate that POLG variation may underly the arrythmia observed in the family, while prior mouse models reported that POLG mutations can induce cardiac fibrosis. Family 5: rare, compound heterozygous missense mutations in ITGB5 were identified as the candidate causative variants in this small family with severe paediatric DCM, possibly affecting adhesion of cardiomyocytes to the extracellular membrane. Conclusion: In total, pathogenic or likely pathogenic mutations were identified in two out of five families studied, while three VUSs with moderate or strong pathogenic potential were identified in two other families. The potential role of POLG in human cardiomyopathy and arrhythmic phenotypes is a finding that should be explored further, as should the putative role of ITGB5 in paediatric cardiomyopathy. This study indicates how exome sequencing, combined with in vivo functional analysis, can identify variants that are likely to contribute to disease in human patients. These techniques may prove useful in bridging the gap in cardiomyopathy knowledge in Africa.